In general, memory units may comprise arrays of hundreds and thousands of memory cells, whereby none of the memory cells may be defective. This imposes severe restrictions on the manufacturing process, and as a consequence, the yield of the manufacturing process might become rather small.
In the prior art, various solutions have been developed for increasing the yield. For example, the memory may be provided with redundant memory cells. If one or more of the memory cells are defective, corresponding redundant memory cells can be activated instead. The redundant memory cells might e.g. be activated by means of fuses, by means of high voltage programming pulses, etc.